The initial energy spectrum of neutrons generated by a neutron source, e.g. a neutron generator or a (thermal) nuclear reactor, which is generally characteristic of said neutron source, is well known. It is common to divide the domains of various energy of the spectrum of neutrons exiting the active core of a nuclear reactor into a thermal range (from 1 meV to 1 eV), an intermedier range (from 1 eV to 100 keV) and a fast neutron range (from 0.1 MeV to 15 MeV), wherein the range from 0.1 MeV to 1.0 MeV is also called epithermal range, while neutrons having a mean energy of about 2.0 MeV are the so-called pile neutrons. Here, and from now on, if it is not stated differently, the term “activation” always refers to activations taking place in the thermal range. In the thermal range, activations take place primarily through the (n, γ) reaction, but (n, p) reactions also appear in this range to a small extent. Moreover, in this energy range, in case of D2 and Be, the (γ, n) reactions, while for Li and Be, the (n, α) reactions also play some role. The (n, f) fission processes will be discussed later. Furthermore, in the intermedier range so-called “resonances” can arise that might also contribute to a small extent to the activation of a target. In case of pile and fast neutrons, the (n, γ) reaction is not a characteristic reaction type and/or further nuclear reactions, for example the (n, 2n) reactions, due to their small efficiency, cannot be utilized on the industrial scale.
At present, neutron activation processes are well known, they are applied in many fields, see e.g. the field of isotope production for various diagnostic purposes. In particular, such solutions are disclosed e.g. by EP Patent No. 0,791,221 B1 and International Publication Pamphlet No. WO2008/060663 A2.